/*
 * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 1999-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: UnionPathIterator.java,v 1.2.4.1 2005/09/14 19:43:25 jeffsuttor Exp $
 */
package com.sun.org.apache.xpath.internal.axes;

import com.sun.org.apache.xml.internal.dtm.Axis;
import com.sun.org.apache.xml.internal.dtm.DTM;
import com.sun.org.apache.xml.internal.dtm.DTMIterator;
import com.sun.org.apache.xpath.internal.Expression;
import com.sun.org.apache.xpath.internal.ExpressionOwner;
import com.sun.org.apache.xpath.internal.XPathVisitor;
import com.sun.org.apache.xpath.internal.compiler.Compiler;
import com.sun.org.apache.xpath.internal.compiler.OpCodes;
import com.sun.org.apache.xpath.internal.compiler.OpMap;

/**
 * This class extends NodeSetDTM, which implements DTMIterator,
 * and fetches nodes one at a time in document order based on a XPath
 * <a href="http://www.w3.org/TR/xpath#NT-UnionExpr">UnionExpr</a>.
 * As each node is iterated via nextNode(), the node is also stored
 * in the NodeVector, so that previousNode() can easily be done.
 *
 * @xsl.usage advanced
 */
public class UnionPathIterator extends LocPathIterator
    implements Cloneable, DTMIterator, java.io.Serializable, PathComponent {

  static final long serialVersionUID = -3910351546843826781L;

  /**
   * Constructor to create an instance which you can add location paths to.
   */
  public UnionPathIterator() {

    super();

    // m_mutable = false;
    // m_cacheNodes = false;
    m_iterators = null;
    m_exprs = null;
  }

  /**
   * Initialize the context values for this expression
   * after it is cloned.
   *
   * @param context The XPath runtime context for this transformation.
   */
  public void setRoot(int context, Object environment) {
    super.setRoot(context, environment);

    try {
      if (null != m_exprs) {
        int n = m_exprs.length;
        DTMIterator newIters[] = new DTMIterator[n];

        for (int i = 0; i < n; i++) {
          DTMIterator iter = m_exprs[i].asIterator(m_execContext, context);
          newIters[i] = iter;
          iter.nextNode();
        }
        m_iterators = newIters;
      }
    } catch (Exception e) {
      throw new com.sun.org.apache.xml.internal.utils.WrappedRuntimeException(e);
    }
  }

  /**
   * Add an iterator to the union list.
   *
   * @param expr non-null reference to a location path iterator.
   */
  public void addIterator(DTMIterator expr) {

    // Increase array size by only 1 at a time.  Fix this
    // if it looks to be a problem.
    if (null == m_iterators) {
      m_iterators = new DTMIterator[1];
      m_iterators[0] = expr;
    } else {
      DTMIterator[] exprs = m_iterators;
      int len = m_iterators.length;

      m_iterators = new DTMIterator[len + 1];

      System.arraycopy(exprs, 0, m_iterators, 0, len);

      m_iterators[len] = expr;
    }
    expr.nextNode();
    if (expr instanceof Expression) {
      ((Expression) expr).exprSetParent(this);
    }
  }

  /**
   * Detaches the iterator from the set which it iterated over, releasing
   * any computational resources and placing the iterator in the INVALID
   * state. After<code>detach</code> has been invoked, calls to
   * <code>nextNode</code> or<code>previousNode</code> will raise the
   * exception INVALID_STATE_ERR.
   */
  public void detach() {
    if (m_allowDetach && null != m_iterators) {
      int n = m_iterators.length;
      for (int i = 0; i < n; i++) {
        m_iterators[i].detach();
      }
      m_iterators = null;
    }
  }


  /**
   * Create a UnionPathIterator object, including creation
   * of location path iterators from the opcode list, and call back
   * into the Compiler to create predicate expressions.
   *
   * @param compiler The Compiler which is creating this expression.
   * @param opPos The position of this iterator in the opcode list from the compiler.
   */
  public UnionPathIterator(Compiler compiler, int opPos)
      throws javax.xml.transform.TransformerException {

    super();

    opPos = OpMap.getFirstChildPos(opPos);

    loadLocationPaths(compiler, opPos, 0);
  }

  /**
   * This will return an iterator capable of handling the union of paths given.
   *
   * @param compiler The Compiler which is creating this expression.
   * @param opPos The position of this iterator in the opcode list from the compiler.
   * @return Object that is derived from LocPathIterator.
   */
  public static LocPathIterator createUnionIterator(Compiler compiler, int opPos)
      throws javax.xml.transform.TransformerException {
    // For the moment, I'm going to first create a full UnionPathIterator, and
    // then see if I can reduce it to a UnionChildIterator.  It would obviously
    // be more effecient to just test for the conditions for a UnionChildIterator,
    // and then create that directly.
    UnionPathIterator upi = new UnionPathIterator(compiler, opPos);
    int nPaths = upi.m_exprs.length;
    boolean isAllChildIterators = true;
    for (int i = 0; i < nPaths; i++) {
      LocPathIterator lpi = upi.m_exprs[i];

      if (lpi.getAxis() != Axis.CHILD) {
        isAllChildIterators = false;
        break;
      } else {
        // check for positional predicates or position function, which won't work.
        if (HasPositionalPredChecker.check(lpi)) {
          isAllChildIterators = false;
          break;
        }
      }
    }
    if (isAllChildIterators) {
      UnionChildIterator uci = new UnionChildIterator();

      for (int i = 0; i < nPaths; i++) {
        PredicatedNodeTest lpi = upi.m_exprs[i];
        // I could strip the lpi down to a pure PredicatedNodeTest, but
        // I don't think it's worth it.  Note that the test can be used
        // as a static object... so it doesn't have to be cloned.
        uci.addNodeTest(lpi);
      }
      return uci;

    } else {
      return upi;
    }
  }

  /**
   * Get the analysis bits for this walker, as defined in the WalkerFactory.
   *
   * @return One of WalkerFactory#BIT_DESCENDANT, etc.
   */
  public int getAnalysisBits() {
    int bits = 0;

    if (m_exprs != null) {
      int n = m_exprs.length;

      for (int i = 0; i < n; i++) {
        int bit = m_exprs[i].getAnalysisBits();
        bits |= bit;
      }
    }

    return bits;
  }

  /**
   * Read the object from a serialization stream.
   *
   * @param stream Input stream to read from
   */
  private void readObject(java.io.ObjectInputStream stream)
      throws java.io.IOException, javax.xml.transform.TransformerException {
    try {
      stream.defaultReadObject();
      m_clones = new IteratorPool(this);
    } catch (ClassNotFoundException cnfe) {
      throw new javax.xml.transform.TransformerException(cnfe);
    }
  }

  /**
   * Get a cloned LocPathIterator that holds the same
   * position as this iterator.
   *
   * @return A clone of this iterator that holds the same node position.
   */
  public Object clone() throws CloneNotSupportedException {

    UnionPathIterator clone = (UnionPathIterator) super.clone();
    if (m_iterators != null) {
      int n = m_iterators.length;

      clone.m_iterators = new DTMIterator[n];

      for (int i = 0; i < n; i++) {
        clone.m_iterators[i] = (DTMIterator) m_iterators[i].clone();
      }
    }

    return clone;
  }


  /**
   * Create a new location path iterator.
   *
   * @param compiler The Compiler which is creating this expression.
   * @param opPos The position of this iterator in the
   * @return New location path iterator.
   */
  protected LocPathIterator createDTMIterator(
      Compiler compiler, int opPos) throws javax.xml.transform.TransformerException {
    LocPathIterator lpi = (LocPathIterator) WalkerFactory.newDTMIterator(compiler, opPos,
        (compiler.getLocationPathDepth() <= 0));
    return lpi;
  }

  /**
   * Initialize the location path iterators.  Recursive.
   *
   * @param compiler The Compiler which is creating this expression.
   * @param opPos The position of this iterator in the opcode list from the compiler.
   * @param count The insert position of the iterator.
   */
  protected void loadLocationPaths(Compiler compiler, int opPos, int count)
      throws javax.xml.transform.TransformerException {

    // TODO: Handle unwrapped FilterExpr
    int steptype = compiler.getOp(opPos);

    if (steptype == OpCodes.OP_LOCATIONPATH) {
      loadLocationPaths(compiler, compiler.getNextOpPos(opPos), count + 1);

      m_exprs[count] = createDTMIterator(compiler, opPos);
      m_exprs[count].exprSetParent(this);
    } else {

      // Have to check for unwrapped functions, which the LocPathIterator
      // doesn't handle.
      switch (steptype) {
        case OpCodes.OP_VARIABLE:
        case OpCodes.OP_EXTFUNCTION:
        case OpCodes.OP_FUNCTION:
        case OpCodes.OP_GROUP:
          loadLocationPaths(compiler, compiler.getNextOpPos(opPos), count + 1);

          WalkingIterator iter =
              new WalkingIterator(compiler.getNamespaceContext());
          iter.exprSetParent(this);

          if (compiler.getLocationPathDepth() <= 0) {
            iter.setIsTopLevel(true);
          }

          iter.m_firstWalker = new com.sun.org.apache.xpath.internal.axes.FilterExprWalker(iter);

          iter.m_firstWalker.init(compiler, opPos, steptype);

          m_exprs[count] = iter;
          break;
        default:
          m_exprs = new LocPathIterator[count];
      }
    }
  }

  /**
   * Returns the next node in the set and advances the position of the
   * iterator in the set. After a DTMIterator is created, the first call
   * to nextNode() returns the first node in the set.
   *
   * @return The next <code>Node</code> in the set being iterated over, or <code>null</code> if
   * there are no more members in that set.
   */
  public int nextNode() {
    if (m_foundLast) {
      return DTM.NULL;
    }

    // Loop through the iterators getting the current fetched
    // node, and get the earliest occuring in document order
    int earliestNode = DTM.NULL;

    if (null != m_iterators) {
      int n = m_iterators.length;
      int iteratorUsed = -1;

      for (int i = 0; i < n; i++) {
        int node = m_iterators[i].getCurrentNode();

        if (DTM.NULL == node) {
          continue;
        } else if (DTM.NULL == earliestNode) {
          iteratorUsed = i;
          earliestNode = node;
        } else {
          if (node == earliestNode) {

            // Found a duplicate, so skip past it.
            m_iterators[i].nextNode();
          } else {
            DTM dtm = getDTM(node);

            if (dtm.isNodeAfter(node, earliestNode)) {
              iteratorUsed = i;
              earliestNode = node;
            }
          }
        }
      }

      if (DTM.NULL != earliestNode) {
        m_iterators[iteratorUsed].nextNode();

        incrementCurrentPos();
      } else {
        m_foundLast = true;
      }
    }

    m_lastFetched = earliestNode;

    return earliestNode;
  }

  /**
   * This function is used to fixup variables from QNames to stack frame
   * indexes at stylesheet build time.
   *
   * @param vars List of QNames that correspond to variables.  This list should be searched
   * backwards for the first qualified name that corresponds to the variable reference qname.  The
   * position of the QName in the vector from the start of the vector will be its position in the
   * stack frame (but variables above the globalsTop value will need to be offset to the current
   * stack frame).
   */
  public void fixupVariables(java.util.Vector vars, int globalsSize) {
    for (int i = 0; i < m_exprs.length; i++) {
      m_exprs[i].fixupVariables(vars, globalsSize);
    }

  }

  /**
   * The location path iterators, one for each
   * <a href="http://www.w3.org/TR/xpath#NT-LocationPath">location
   * path</a> contained in the union expression.
   *
   * @serial
   */
  protected LocPathIterator[] m_exprs;


  /**
   * The location path iterators, one for each
   * <a href="http://www.w3.org/TR/xpath#NT-LocationPath">location
   * path</a> contained in the union expression.
   *
   * @serial
   */
  protected DTMIterator[] m_iterators;

  /**
   * Returns the axis being iterated, if it is known.
   *
   * @return Axis.CHILD, etc., or -1 if the axis is not known or is of multiple types.
   */
  public int getAxis() {
    // Could be smarter.
    return -1;
  }

  class iterOwner implements ExpressionOwner {

    int m_index;

    iterOwner(int index) {
      m_index = index;
    }

    /**
     * @see ExpressionOwner#getExpression()
     */
    public Expression getExpression() {
      return m_exprs[m_index];
    }

    /**
     * @see ExpressionOwner#setExpression(Expression)
     */
    public void setExpression(Expression exp) {

      if (!(exp instanceof LocPathIterator)) {
        // Yuck.  Need FilterExprIter.  Or make it so m_exprs can be just
        // plain expressions?
        WalkingIterator wi = new WalkingIterator(getPrefixResolver());
        FilterExprWalker few = new FilterExprWalker(wi);
        wi.setFirstWalker(few);
        few.setInnerExpression(exp);
        wi.exprSetParent(UnionPathIterator.this);
        few.exprSetParent(wi);
        exp.exprSetParent(few);
        exp = wi;
      } else {
        exp.exprSetParent(UnionPathIterator.this);
      }
      m_exprs[m_index] = (LocPathIterator) exp;
    }

  }

  /**
   * @see com.sun.org.apache.xpath.internal.XPathVisitable#callVisitors(ExpressionOwner,
   * XPathVisitor)
   */
  public void callVisitors(ExpressionOwner owner, XPathVisitor visitor) {
    if (visitor.visitUnionPath(owner, this)) {
      if (null != m_exprs) {
        int n = m_exprs.length;
        for (int i = 0; i < n; i++) {
          m_exprs[i].callVisitors(new iterOwner(i), visitor);
        }
      }
    }
  }

  /**
   * @see Expression#deepEquals(Expression)
   */
  public boolean deepEquals(Expression expr) {
    if (!super.deepEquals(expr)) {
      return false;
    }

    UnionPathIterator upi = (UnionPathIterator) expr;

    if (null != m_exprs) {
      int n = m_exprs.length;

      if ((null == upi.m_exprs) || (upi.m_exprs.length != n)) {
        return false;
      }

      for (int i = 0; i < n; i++) {
        if (!m_exprs[i].deepEquals(upi.m_exprs[i])) {
          return false;
        }
      }
    } else if (null != upi.m_exprs) {
      return false;
    }

    return true;
  }


}
